Hollywood invariably and regularly forgets that older people like to go to movies. A “Hope Springs” or “Best Exotic Marigold Hotel” will surface once or twice a year, earn $60 to $80 million – a fair profit on a modest budget – and make no impression on executives. So “Quartet” will probably come and go with a similar lack of attention, which will be a small pity.

I can’t recall the last film I saw where the writer, director and all top-billed actors were 70 or older. (Billy Connolly was 69 during the shooting but turned 70 in November.) Though that’s true here – and virtually all the supporting players are that age – there’s no lack of vitality, just a lack of furor. Ronald Harwood has adapted his own slender play into a quietly appealing story.

Life at the Thomas Beecham House gets bumpy even before soprano Jean Horton (Maggie Smith) comes to live there. The home for retired musicians may close if an upcoming gala doesn’t raise enough money, and residents are expected to do their part.

Tenor Reginald Paget (Tom Courtenay), baritone Wilf Bond (Connolly) and mezzo Cissy Robson (Pauline Collins) are thrilled to see Jean unloading her bags: Now they can reproduce the Act 4 quartet from the famous “Rigoletto” they recorded when all were stars in the 1970s. But Jean, ashamed of the quality of her voice, refuses to sing in front of the people with whom she competed – and, by inference, abused – in her diva days. That Reggie divorced her long ago only increases underlying animosity.

Harwood’s best screenplays (“The Dresser,” “The Pianist,” “Being Julia”) have dealt with the egos, fears and insecurities of performers. He, like his characters, has grown less ambitious with age: This film toddles sweetly toward its inevitable ending.

So the performances provide all the pleasure: Connolly is permitted to steal scenes as a sexually charged old man who may be boasting, and Collins’ descent into Alzheimer’s blankness is well done. Nobody beats Courtenay at soft-spoken worriers or Smith at frosty characters who are waiting to be thawed.

Fans of British music and theater will especially enjoy cameos by retired actors, singers and instrumentalists. (Stay for the credits to see who they are.) Gwyneth Jones has the largest of these parts and sings a “Vissi d’arte” (from “Tosca”) with the same warmth and wobble in her voice as she had 30 years ago.

Dustin Hoffman makes his official feature directing debut at 75, a fact that fits in with the film’s oft-repeated motto: “Old age is not for sissies.” (He did uncredited directing work on the underrated “Straight Time” in 1978.)

Hoffman and Harwood aren’t afraid to show us old people who are rude, demanding, unreasonable and foolish, though the final overall mood remains blissful. Hoffman might have more to say as a director, if anyone in Hollywood cares to find out.